The addition of a hydrazine compound to a silver halide photographic emulsion or a developing solution is known in U.S. Pat. Nos. 3,730,727 (the developing solution in which ascorbic acid and hydrazine are combined), 3,227,552 (hydrazine is used as an auxiliary developing agent for obtaining a direct positive color image), 3,386,831 (.beta.-monophenylhydrazide of aliphatic carboxylic acid is contained as a stabilizer for a silver halide light-sensitive material), and 2,419,975, and The Theory of Photographic Process written by Mees, the third edition (1966 ), p. 281.
Among them, it is disclosed particularly in U.S. Pat. No. 2,419,975 that a hydrazine compound is added to obtain a negative image with a hard gradation.
It is described in the same patent specification that the addition of the hydrazine compound to a silver bromochloride emulsion and a development in a developing solution having as high pH as 12.8 provide a very hard gradation photographic characteristic with gamma (.gamma.) exceeding 10. However, the strong base developing solution having pH close to 13 is susceptible to an air oxidation and is instable. Accordingly, it can not endure storing and use for a long time.
An ultra high gradation photographic characteristic with gamma exceeding 10 is very useful for the photo-graphic reproduction of a continuous image with a dot image useful for a printing plate making or the reproduction of a line drawing either in a negative image or a positive image. There has so far generally been used for such the purpose, the method in which a silver bromochloride emulsion having a silver chloride content exceeding 50 mole% preferably 75 mole% is used to carry out a development in a hydroquinone developing solution having the effective concentration of a sulfurous acid ion set at a very low level (usually 0.1 mole/liter or less). However, because of the low sulfurous acid ion concentration in the developing solution in this method, the developing solution is very unstable and can not endure a storing exceeding three days.
Further, since these methods require to use the silver bromochloride emulsion having the relatively high silver chloride content, a high sensitivity has not been able to obtain. Accordingly, it has strongly been desired to use a high sensitive emulsion and a stable developing solution to obtain a ultrahard gradation photographic characteristic useful for the reproduction of a halftone dot image and a line drawing.
In U.S. Pat. Nos. 4,224,401, 4,168,977, 4,243,739, 4,272,614, and 4,323,643, the silver halide emulsions providing the very hard gradation negative photographic characteristics with a stable developing solution are disclosed. However, it has been known that the acylhydrazine compounds used therein have several defects.
That is, it is known that these conventional hydrazines generate a nitrogen gas during a development processing, and these gases are concentrated in a film to form bubbles and damage a photographic image. Further, they are eluted in a development processing solution to exert an adverse affect to a photographic material.
It has so far been known as the means for preventing the elution to the development processing solution to increase the molecular weight of a nucleus forming agent to provide it with an anti-diffusion character. However, it has come to be known that the problem on an aging stability is involved in a conventional anti-diffusible nucleus forming agent. That is, the aging of a coating solution containing the nucleus forming agent generates a deposit in the coating solution to deteriorate a filtering performance and further changes the photographic performances.
In the case where a lot of these conventional hydrazines is required for a sensitization and a hard gradation and a particularly high sensitivity is required to the performances of a light-sensitive material, the combined use with the other sensitizing techniques (for example, enhancing a chemical sensitization, increasing a grain size, and adding the compounds accelerating a sensitization as described in U.S. Pat. Nos. 4,272,606, and 4,241,164) generally causes an aging sensitization and the increase in a fog during a storage in some cases.
Accordingly, there have been desired the compounds which can reduce the generation of bubbles and the elution to a developing solution, have no problems on an aging stability, and provide a very hard gradation photographic characteristic with the addition of a very small amount.
Further, it is described in U.S. Pat. Nos. 4,385,108, 4,269,929, and 4,243,739 that hydrazines having a substituent easily adsorbing on a silver halide grain can be used to obtain a photographic performance with a very hard negative gradation. However, those concretely described in the above exemplified compounds among the hydrazine compounds having an adsorbing group have the problem that they cause an aging desensitization during a storage. Accordingly, it was required to select the compounds causing no such the problem.
Meanwhile, the direct positive photographic processes are variously available, and most useful are the process in which the silver halide grains fogged in advance are exposed under the presence of a desensitizer and then developed, and the process in which the silver halide emulsion having a light-sensitive nucleus mainly in the inside of a silver halide grain is exposed and then developed under the presence of a nucleus forming agent. The present invention relates to the latter. The silver halide emulsion which has the light-sensitive nucleus mainly in the inside of the silver halide grain and in which a latent image is formed mainly in the inside of the grain is called an inner latent image type silver halide emulsion, and it can be distinguished from the silver halide grains forming the latent image mainly on a grain surface.
There are known the process in which the internal latent image type silver halide photographic emulsion is subjected to a surface development under the presence of a nucleus forming agent to obtain a direct positive image, and the photographic emulsions or light-sensitive materials used for such the process.
In the above method for obtaining the direct positive image, the nucleus forming agent may be added to a developing solution. A better reversal characteristic can be obtained when it is added to the photographic emulsion layer or other suitable layers of a light-sensitive material to adsorb it on a silver halide grain surface.
There are known as the nucleus forming agent used for the above method for obtaining the direct positive image, hydrazines described in U.S. Pat. Nos. 2,563,785 and 2,588,982; the hydrazine and hydrazide series compounds described in U.S. Pat. No. 3,227,552; the heterocyclic quaternary salt compounds described in U.S. Pat. Nos. 3,615,615, 3,719,494, 3,734,738, 4,094,683, and 4,115,122, British Patent 1,283,835, and JP-A-52-3426 (the term "JP-A" as used herein means an unexamined published Japanese patent application) and 52-69613; the thiourea combining type acylphenylhydrazine series compounds described in U.S. Pat. Nos. 4,030,925, 4,031,127, 4,139,387, 4,245,037, 4,255,511, and 4,276,364, and British Patent 4,012,443; the compounds having heterocyclic thioamide as an adsorbing group, described in U.S. Pat. No. 4,080,207; the phenylacylhydrazine compounds having a heterocyclic group having a mercapto group as an adsorbing group, described in British Patent 2,011,397B; the sensitizing dyes having a substituent having a nucleus forming action in a molecular structure, described in U.S. Pat. No. 3,718,470; and the hydrazine compounds described in JP-A-59-200230, JP-A-50-212828, and JP-A-59-212829, and Research Disclosure No. 23510 (November 1953).
However, it has come to be found that there are involved therein the defects that any of these compounds have an insufficient activity as the nucleus forming agent and those having a high activity have an insufficient storing performance and that after they are added to an emulsion, the activities thereof are changed before coating and further the addition of a lot thereof deteriorates a membrane quality.
There are proposed for the purpose of solving these defects, the adsorptive type hydrazine derivatives described in JP-A-60-179743, JP-A-61-170733, JP-A-62-65034, JP-A-62-948, and JP-A-61-270744; the hydrazine derivatives having a heteroaromatic ring residue in a molecule, described in JP-A-62-275247; or the hydrazine derivatives having a group for a modification, described in JP-A-62-270948 and JP-A-63-29751. However, there used to be involved therein the problems that any of them has an insufficient nucleus forming activity for the requirements to lower pH of a development processing solution in order to increase the stability of the processing solution (that is, to prevent the deterioration of a developing agent), to shorten a processing time in a development, or to decrease a dependency on the fluctuation of a developing solution composition (for example, pH and sodium sulfite) and that an adverse influence due to the elution to the development processing solution can be seen.
Accordingly, a first object of the present invention is to provide a silver halide photographic material capable of providing a very hard gradation photographic characteristic having a gamma exceeding 10 in a stable developing solution.
A second object of the present invention is to provide a negative type silver halide photographic material containing high activity hydrazines capable of providing a desired very hard gradation photographic characteristic even in a low pH developing solution at a small addition amount without exerting an adverse influence to the photographic performances.
A third object of the present invention is to provide a direct positive type silver halide photographic material containing high activity hydrazines capable of providing an excellent reversal characteristic even in the low pH developing solution.
A fourth object of the present invention is to provide a silver halide photographic material containing hydrazines which can easily be synthesized and have an excellent storing performance and having a good aging stability.
A fifth object of the present invention is to provide a silver halide photographic material in which an emulsion has a good aging stability and an activity fluctuation in manufacturing the light-sensitive material is small.